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981.
982.
Huge parallel high-performance computing (HPC) architectures are today available laboratories for modelling atomic forces with high accuracy and for large samples of atoms. Modern statistical tools allow to simulate the statistics of these samples, while first-principles molecular dynamics (MD) can probe the interactions within large atomic samples, including possible chemical reactions. But a proper statistical convergence for the ensemble, represented in terms of a bundle of trajectories, is still unsatisfactory in terms of comparisons with experiments. Can we learn something by these HPC experiments? In this contribution, we show one example, where the occurrence of a chemical reaction in a disordered system is probed. The complex of the copper ion and a segment of the amyloid-β peptide, of wide interest in understanding the progress of Alzheimer's disease, was modelled combining constructions based on empirical force fields with first-principles MD simulations. We simulate a bundle of 16 different structures, biasing different Cu coordination numbers and changing the charge (oxidation state) of the assembly. Even within the given approximations for forces and the poor sampling, we could identify the structures of the complex that are able to react with hydrogen peroxide. The observation explains, at a molecular level, one important linkage between Alzheimer's disease and oxidative stress. This is an example of a general strategy for exploiting reactive configurations within a large set of possible reasonable candidates. 相似文献
983.
Valérie Prouzet-Mauléon Christelle Monribot-Espagne Hélian Boucherie Gilles Lagniel Sébastien Lopez Jean Labarre Jérome Garin Guy J-M Lauquin 《The Journal of biological chemistry》2002,277(7):4823-4830
Yeasts lacking cytoplasmic superoxide dismutase (Cu,Zn-SOD) activity are permanently subjected to oxidative stress. We used two-dimensional PAGE to examine the proteome pattern of Saccharomyces cerevisiae strains lacking Cu,Zn-SOD. We found a new stable form of alkyl hydroperoxide reductase 1 (Ahp1) with a lower isoelectric point. This form was also present in wild type strains after treatment with tert-butyl hydroperoxide. In vitro enzyme assays showed that Ahp1p had lower specific activity in strains lacking Cu,Zn-SOD. We studied three mutants presenting a reduced production of the low pI variant under oxidative stress conditions. Two of the mutants (C62S and S59D) were totally inactive, thus suggesting that the acidic form of Ahp1p may only appear when the enzyme is functional. The other mutant (S59A) was active in vitro and was more resistant to inactivation by tert-butyl hydroperoxide than the wild type enzyme. Furthermore, the inactivation of Ahp1p in vitro is correlated with its conversion to the low pI form. These results suggest that in vivo during some particular oxidative stress (alkyl hydroperoxide treatment or lack of Cu,Zn-SOD activity but not hydrogen peroxide treatment), the catalytic cysteine of Ahp1p is more oxidized than cysteine-sulfenic acid (a natural occurring intermediate of the enzymatic reaction) and that cysteine-sulfinic acid or cysteine-sulfonic acid variant may be inactive. 相似文献
984.
García-Echeverría Carlos Stamm Christelle Wille Roman Arz Dorothee Gay Brigitte 《International journal of peptide research and therapeutics》1997,4(1):49-53
Summary A series of biotinylated phosphopeptides has been synthesized and used in the development of an ELISA-based approach to assess
SH2/PTB-phosphoprotein interactions in vitro in terms of affinity and specificity.
Abbreviations: BSA, bovine serum albumin; DMSO, dimethylsulfoxie; EGF, epidermal growth factor; ELISA, enzyme-linked immunosorbent assay;
HATU,N-[(dimethylamino)1H-1,2,3-triazolo[4,5-b]pyridin-1-ylmethylene]-N-methylmethan-aminium hexafluorophosphateN-oxide; HPLC, high-performance liquid chromatography; GST, glutathione-S-transferase; pY, phosphotyrosine; TFA, trifluoroacetic acid; Tris, tris(hydroxymethyl)aminomethane; TBS-T, Tris buffered
saline Tween. The abbreviations used for amino acids follow the recommendations of the IUPAC-IUB Commission of Biochemical
Nomenclature [Eur. J. Biochem., 138 (1984) 9]. 相似文献
985.
Mutation in splicing consensus sequences causes lack of TCR membrane expression due to exon excision
T-cell antigen receptor (TCR) membrane-negative T-cell mutants can be divided into two groups: 1) those which lack one of
the six TCR polypeptides and 2) those which contain a mutated TCR chain. The present experiments reveal a new mechanism for
the development of TCR membrane-negative T-cell variants: mutations in splicing consensus motifs causing excision or misreading
of an entire exon (exon 3 of the TCRAC or TCRBC genes). C27.15 cells transcribe a TCR α chain consisting of TCRAVJCexon1Cexon2-encoded amino acids plus six new amino acids. The assembly defect seems to be that the truncated α chain does not interact
with CD3 δ molecules; consequently, no TCR αβ/CD3 δεγε complexes are formed. E6.E12 cells transcribe a TCR β chain composed
of TCRBVDJCexon1Cexon2-encoded amino acids plus twenty-seven new amino acids, which seem not to form a transmembrane region. The truncated β chain
does associate with CD3 γε heterodimers, yet no TCR αβ/CD3 δεγε complexes are made. This may be due either to low assembly
of TCR β/CD3 γε trimers or to lack of access of the mutated TCR β/CD3 γε trimers to the TCR α/CD3 δε compartment in the endoplasmic
reticulum.
Received: 25 September 1996 / Revised: 7 November 1996 相似文献
986.
Felana Harilanto Andrianjakarivony Yvan Bettarel Philippe Cecchi Sonia Bouchard Emily Chase Christelle Desnues 《Environmental microbiology》2023,25(11):2368-2387
Human and livestock sewage is one of the major causes of excess nutrients, leading to the eutrophication of aquatic ecosystems and potentially to the emergence or spread of pathogenic viruses. This study aimed to investigate the composition and diversity of aquatic viromes in a highly anthropized lagoon, to identify the presence of pathogenic taxa and to explore their use as possible viral indicators of faecal contamination. For this, water and sediment samples were collected in the Ebrié Lagoon (Ivory Coast) at seven stations with contrasting levels of eutrophication. The DNA viromes of the planktonic and the benthic compartments were highly divergent, but were not influenced by the level of eutrophication. Conversely, the RNA viromes in the water column were comparable to those found in sediment, but showed significant differences between the stations. We detected the presence of viral DNA and RNA sequences we had assigned as indicators of faecal contamination (smacovirus, pecovirus and pepper mild mottle virus) as well as human pathogens (human cyclovirus, coxsackie B virus and picobirnavirus), which were all enriched in the most eutrophicated sites. These findings suggest that the examination of viromes represents a promising tool for assessing the state of human-induced contamination of aquatic ecosystems. 相似文献
987.
Jean-Luc Tholozan Jean-Philippe Grivet Christelle Vallet 《Archives of microbiology》1994,162(6):401-408
Pectinatus frisingensis, a recently described species of anaerobic mesophilic beer-spoilage bacteria, grows by fermenting various organic compounds,
and produces mainly propionate, acetate, and succinate. Although acrylate and succinate were both dismutated by dense resting-cell
suspensions, propionate production proceeded through the succinate pathway: [3-13C]pyruvate consumption led to equal 13C-labeling of propionate on methyl and methylene groups. Growth on glucose or glycerol led to a similar propionate to acetate
ratio, suggesting dihydroxyacetone phosphate as being a common metabolic intermediate. Diacetyl, 1,3-propanediol, and 2,3-butanediol
were not growth substrates or fermentation products, but they were all dismutated by dense resting-cell suspensions to acetate
and propionate. Acetoin was a minor fermentation product. The consumption of [2-13C] or [3-13C]pyruvate by dense resting-cell suspensions demonstrated the involvement of two equivalent pyruvate molecules during acetoin
production. Key enzymes involved in this metabolism were measured in anoxic cell-free extracts. A tentative metabolic pathway
to the main fermentation products was proposed from the above results.
Received: 17 February 1994 / Accepted: 30 August 1994 相似文献
988.
David R. Horton Christelle Guédot & Peter J. Landolt 《Entomologia Experimentalis et Applicata》2007,123(2):185-192
A companion study showed that male pear psylla, Cacopsylla pyricola (Förster) (Homoptera: Psyllidae) were attracted to volatiles from pear shoots infested with post-diapause females. The present study compared the behavioral response of males to diapause and post-diapause females. Assays were done using a Y-tube olfactometer. We collected male and female winterform psylla from pear orchards at regular intervals between late October (early diapause) and late February (post-diapause). Female-infested shoots were not attractive to males until the February samples, coinciding with ovarian maturation and onset of mating in the field. A second set of assays was done in which we manipulated diapause status in the laboratory either by exposing psylla to a long-day photoperiod or by treating insects with an insect growth regulator, fenoxycarb. In the photoperiod experiments, both short-day and long-day males preferentially selected long-day (post-diapause) females over short-day (diapause) females. Fenoxycarb-treated males preferred fenoxycarb-treated (post-diapause) females over untreated (diapause) females; untreated males showed no preferences. Results support observations made elsewhere that male winterform pear psylla perceive and are attracted to volatile odors associated with pear shoots infested with post-diapause females. 相似文献
989.
Novel insights into the relationships between dendritic cell subsets in human and mouse revealed by genome-wide expression profiling 总被引:2,自引:0,他引:2
990.
Christine Chabrolle Eric JeanPierre Lucie Tosca Christelle Ramé Joëlle Dupont 《Reproductive biology and endocrinology : RB&E》2008,6(1):11